How getters solve encapsulation

encapsulation.php

<?php

calss Date {
  public $date;
  
  public function __construct( $date){
    $this->date = $date;
  }
  
  //other methods
}

class Man {
  public $dob ;
  
  public function __construct( Date $dob){
    $this->dob = $dob;
  }
}

//I can easily do this:
$man = new Man( new Date( '01/01/1990'));
$man->dob->date = '01/01/1716'; //My $man is now a vampire

class YoungMan {
  private $dob;
  
  public function __construct( Date $dob){
    $this->dob = $dob;
  }
  
  /**
   * External code can only get a copy of the $dob field.
   * Changeing it does not affect the internal state of the YoungMan object
   */
  public function getDob(){
    return new Date( $this->dob->date);
  }
  
  public function setDob( Date $newDob){
    //check the date to see if it's within 'human' range
    //if it is, set it
    //if not throw a new Exception
  }
  
}

//now when you do
$youngMan = new YoungMan( new Date( '01/01/2000'));

//you cant's do $youngMan->dob->date = '01/01/2050'
//you have to do
$youngManDOB = $youngMan->getDob();
//you can do
$youngManDOB->date = '01/01/2050';
//but that doesn't affect the DOB of $youngMan
//in order to affect that, you have to do
$youngMan->setDob( new Date('01/01/2050'));
//if the new date is not within the accepted range,
//an Exception will be thrown, but the internal state of $youngMan is preserved